The invention relates to a method and an apparatus for the introduction of insertion objects into multi-sheet products, particularly into multi-sheet printed products.
A multi-sheet printed product consists of a plurality of sheets, for example rectangular sheets of paper, which (when the product is in the closed state) are joined together to form a stack and are held together in the region of one edge. Each of the sheets thus has an edge (fixed edge) which cannot be separated from the corresponding edges of other sheets and, for example, three edges (separable edges) which can be separated from the corresponding edges of the other sheets. A multi-sheet product is, for example, opened by pushing an opener between the sheets in such a manner that a number of sheets are turned, relative to another number of sheets or to the remainder of the sheets, about an axis parallel to the fixed edges of the sheets, such that two or more stacks of sheets are formed.
The fixed edges of multi-sheet printed products can be held together by for example one or more folds lying one in the other, binding, stitching or by a tool which is not part of the printed product and which holds the edges together temporarily. Newspapers, periodicals, books, brochures, sheets folded one into the other, or stacks of loose sheets temporarily held together are therefore all multi-sheet printed products.
Inserters are introduced for various purposes between the sheets of multi-sheet printed products. For example, openers are inserted in order to open the products, so that supplements can be pushed in. For this purpose sheet edges lying on one another in the closed product are usually first separated from each other at at least one point, in such a manner that a space, into which an opener is then inserted, is formed at least between two neighbouring sheets in the product and at least in the region of one of their separable edges. Through the insertion of the opener the sheets, or a part of them, are turned around the fixed edge, that is to say the printed product is opened and, if necessary, held in this open position.
It is advantageous for the edges to be separated, before the opener is inserted, at a point as far as possible from the fixed edge of the sheets.
If, for example, a supplement is to be inserted into the opened printed product, use is usually made of an opener provided with an insertion slot, the latter being disposed substantially parallel to the fixed edge of the multi-sheet printed product and the supplement being inserted through the insertion slot.
Various methods and devices are known for the insertion of openers into continuously conveyed multi-sheet products, particularly printed products, these methods and devices providing as a first step the separation of at least pact of the edges of the sheets and, as a second step, the insertion of the opener between the separated edges. Some of these methods and devices will be briefly recalled.
As an example, suction is applied, at a point distant from the fixed edges, to the upper side of multi-sheet printed products which are being conveyed in a horizontal position, in order to raise the uppermost sheet for an insertion operation. By this method multi-sheet printed products can be opened only between the uppermost sheet and the remainder of the sheets.
According to Swiss Patent Specification No. 584153 the sheets of a folded printed product are pressed together by a pressure member, so that the prestress produced in the sheets by the folding presses the separable sheet edges apart and thus an inserter can be pushed between them. The method can be applied only to folded products of a determined kind and the insertion object can be introduced only in the middle.
According to European Patent Specification No. 80185 products with prefold (sheets not folded exactly in the middle) or corresponding products having narrower and wider sheets are opened by buckling the wider sheets, so that they arch up against the narrower sheets and the latter consequently move apart, and thus the corresponding edges are separated and an opener can be introduced. This method can be applied only to products having sheets of different widths (for example with prefold) and sheets which can be deformed without being damaged. The product is always opened between the narrower and the wider sheets, so that a product with prefold is always opened in the middle.
According to Swiss Patent Specification No. 521911 a printed product, conveyed in a horizontal position with the fixed edges of the sheets at the rear (referring to the conveying direction), is opened by introducing from above a braking force which retards the top sheets relative to the bottom sheets and thus separates the corresponding edges, between which an opener can then be inserted. This method can also be used only for products whose sheets can be deformed without damage. A folded product is opened centrally by this method. In order to ensure opening at a determined different point, the corresponding sheets must be pretreated at the sides lying one on the other, so that their mutual friction is reduced.
The methods and apparatuses described are all restricted in use to multi-sheet products having determined properties and are suitable only for an insertion operation at a clearly defined point (for example in the middle). For the opening of multi-sheet products of any kind, without requiring pretreatment of the sheets while nevertheless permitting opening between any two predetermined sheets, the methods according to the two Swiss Patent Specifications Nos. 641113 and 644815 are available, both of them being based on the introduction of a pointed edge separator between sheet edges of the closed printed product which lie one on the other. In the first case the edge separator obstructs the movement of a number of sheets, which thus arch up at at least one point, whereby the other sheets are raised and thus deflected on an opener. In the second case a movement of the edge separator inserted between the sheets in order to separate the sheet edges separates a number of sheets from the other sheets, so that an opener can be inserted. In both cases the distance between the edge-separating point of the edge separator and the surface on which the printed product is supported defines the place where the printed product is opened.
The disadvantage common to these two methods consists in that the sheet edges lying one on the other are separated by the insertion of a pointed object, which can easily lead to damage to the sheets. Furthermore, depending on the quality of the finish of the product to be opened, the accuracy of insertion is more or less limited.
The problem underlying the invention is now that of indicating a method by which insertion objects, for example openers, can be introduced into multi-sheet products, particularly printed products, between any predeterminable sherbets. The method and apparatus should be applicable very largely irrespective of the type of connection between the fixed edges of the sheets (folding, stitching, binding, temporary fastening, and so on), very largely irrespective of the mechanical properties of the sheets (deformability, stiffness, friction), and very largely irrespective of the number of sheets contained in the product. In particular, the method should also be applicable to continuously conveyed products. The method should also make it possible for insertion objects to be introduced simultaneously at more than one point into products having a corresponding number of sheets. The apparatus to be provided for carrying out the method according to the invention should be simple and able to be integrated into existing equipment for the further processing of multi-sheet products in a more or less opened state, for example apparatuses for inserting supplements.